ED Note: This is precision work – if you are not experienced with fine soldering, I would not try this technique – Joe.
The method to solder L1 Bridges can be summarized as follow:
1) Protect the other bridge with some tape.
2) Use a soldering iron with a 2 or 3 mm large tip. We set the temperature at nearly 350°C.
First, we used the smallest iron tip available (1/2 mm), but the “quantity of heat” transferred to the small L1 bridge was not high enough to allow “real” soldering. So we changed for a larger one (2 or 3 mm and same temperature). It seems that the ceramic (processor) absorbs heat very fast. The larger tip will transfer faster, higher temperatures that allow good soldering. Also you have to proceed “fast”, it is not a cooking operation!
The L1 bridge are a little bit difficult to solder while they get not “hot” enough. I could see that some “mechanical” operation by rubbing the tinned tip over the L1 bridge could tinning the golden bridge too. When that bridge are tinned, it is very easy to place the solder joint over the laser cut.
The use of soldering liquid desoxident allow easier task (in French “flux de soudure liquide” not in my dictionary).
Not shown, but used, some laboratory binocular that zoom the work by 2 or 3 (even with good vision , it’s a small work!)
3) When the soldering temperature is high enough, the large tip is used and some “flux de soudure”, there is NO chance to connect all bridge together. Even the small cut (gap) on the L1 bridge are a little bit difficult to fill. You can find the result on the following picture:
The Thunderbird 750 we upgraded could reach 925 MHz with 1.75 core voltage.
C. H. Hoffman – France